/*
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 *    Arithmetic.java
 *    Copyright (C) 2008-2012 University of Waikato, Hamilton, New Zealand
 *
 */

package weka.core.pmml;

import java.util.ArrayList;

import weka.core.Attribute;

/**
 * Built-in function for +, -, *, /.
 * 
 * @author Mark Hall (mhall{[at]}pentaho{[dot]}com)
 * @version $Revision 1.0 $
 */
public class BuiltInArithmetic extends Function {

    /**
     * For serialization.
     */
    private static final long serialVersionUID = 2275009453597279459L;

    /**
     * Enumerated type for the operator.
     */
    enum Operator {
        ADDITION(" + ") {
            double eval(double a, double b) {
                return a + b;
            }
        },
        SUBTRACTION(" - ") {
            double eval(double a, double b) {
                return a - b;
            }
        },
        MULTIPLICATION(" * ") {
            double eval(double a, double b) {
                return a * b;
            }
        },
        DIVISION(" / ") {
            double eval(double a, double b) {
                return a / b;
            }
        };

        abstract double eval(double a, double b);

        private final String m_stringVal;

        Operator(String opName) {
            m_stringVal = opName;
        }

        public String toString() {
            return m_stringVal;
        }
    }

    /** The operator for this function */
    protected Operator m_operator = Operator.ADDITION;

    /**
     * Construct a new Arithmetic built-in pmml function.
     * 
     * @param op the operator to use.
     */
    public BuiltInArithmetic(Operator op) {
        m_operator = op;
        m_functionName = m_operator.toString();
    }

    /**
     * Set the structure of the parameters that are expected as input by this
     * function. This must be called before getOutputDef() is called.
     * 
     * @param paramDefs the structure of the input parameters
     * @throws Exception if the number or types of parameters are not acceptable by
     *                   this function
     */
    public void setParameterDefs(ArrayList<Attribute> paramDefs) throws Exception {
        m_parameterDefs = paramDefs;

        if (m_parameterDefs.size() != 2) {
            throw new Exception("[Arithmetic] wrong number of parameters. Recieved " + m_parameterDefs.size() + ", expected 2.");
        }
    }

    /**
     * Returns an array of the names of the parameters expected as input by this
     * function
     * 
     * @return an array of the parameter names
     */
    public String[] getParameterNames() {
        String[] result = { "A", "B" };
        return result;
    }

    /**
     * Get the structure of the result produced by this function. Subclasses must
     * implement.
     * 
     * @return the structure of the result produced by this function.
     */
    public Attribute getOutputDef() {
        return new Attribute("BuiltInArithmeticResult:" + m_operator.toString());
    }

    /**
     * Get the result of applying this function.
     * 
     * @param incoming the arguments to this function (supplied in order to match
     *                 that of the parameter definitions
     * @return the result of applying this function. When the optype is categorical
     *         or ordinal, an index into the values of the output definition is
     *         returned.
     * @throws Exception if there is a problem computing the result of this function
     */
    public double getResult(double[] incoming) throws Exception {
        if (m_parameterDefs == null) {
            throw new Exception("[BuiltInArithmetic] incoming parameter structure has not been set!");
        }

        if (m_parameterDefs.size() != 2 || incoming.length != 2) {
            throw new Exception("[BuiltInArithmetic] wrong number of parameters!");
        }

        double result = m_operator.eval(incoming[0], incoming[1]);

        return result;
    }

    public String toString() {
        return toString("");
    }

    public String toString(String pad) {
        return pad + m_parameterDefs.get(0).name() + m_functionName + m_parameterDefs.get(1).name();
    }
}
